This script sends a message with Pushover if no one is attached to a given screen.
/set pushover_silence: Defines how long irssi waits before a new push message is sent.
/set pushover_screensession: Your screen session. irssi if you use screen -S irssi.
/set pushover_usertoken: Your Pushover User Token.
/set pushover_apptoken: Your Pushover Application Token.